High temperature low thermal expansion ceramic

Abstract

This invention relates to the high temperature stabilization of aluminum titanate and aluminum titanate-mullite compositions by the addition of iron oxide. It has been found that iron oxide concentrations greater than 5 weight percent and as high as approximately 25 weight percent have a stabilization effect at high temperatures on aluminum titanates. The resultant ceramic body is further enhanced by the addition of from 0.1 to 5 weight percent rare earth oxide.

We claim: 
     
       1. A sintered ceramic article containing iron-aluminum titanate solid solution and mullite as the predominant crystal phases with a minor amount of a rare earth metal oxide crystal phases, said article exhibiting grain boundary and intracrystalline microcracking and consisting essentially, expressed in terms of weight percent on the oxide basis, of 1.5-20% SiO 2 , 225-25% Fe 2  O 3 , 35-75% Al 2  O 3 , 10-40% TiO 2 , and 0.1-5% RE 2  O 3 . 
     
     
       2. A sintered ceramic article according to claim 1 wherein said crystal phases, expressed in terms of volume percent, consist essentially of about 25-90% iron-aluminum titanate solid solution and about 5-70% mullite with the rare earth metal oxide comprising up to the remainder. 
     
     
       3. A sintered ceramic body as in claim 2 wherein said solid solution consists essentially of, by weight percent, 30 to 75 percent alumina, 20 to 65 percent titania, and >5 to 25 percent iron oxide. 
     
     
       4. A sintered ceramic body as in claim 3 wherein said solid solution is stable to within less than 20 percent of a total stoichiometric decomposition, wherein said decomposition products are Al 2  O 3 , Fe 2  O 3 , and TiO 2 , within the temperature range between approximately 1000° C. to 1300° C. 
     
     
       5. A sintered ceramic body as in claim 1 wherein said rare earth oxide is selected from the group consisting essentially of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, erbium, ytterbium, yttrium, scandium, and/or a combination thereof. 
     
     
       6. A sintered ceramic body as in claim 1 wherein said body exhibits a coefficient of thermal expansion between -25×10 -7  /°C. and 25×10 -7  /°C. (25°-800° C.). 
     
     
       7. A sintered ceramic body as in claim 1 wherein said body exhibits a four point bend MOR in the range from 1000 psi to 9000 psi. 
     
     
       8. A sintered ceramic body as in claim 1 wherein said body exhibits a coefficient of thermal cycling growth of less than 200×10 -4  percent per cycle. 
     
     
       9. A sintered ceramic body as in claim 1 wherein said body is a honeycomb. 
     
     
       10. A sintered ceramic body consisting essentially of, by weight percent, 50 to 75 percent iron-aluminum titanate solid solution, 20 to 50 percent mullite, and 0.1 to 5 percent rate earth oxide. 
     
     
       11. A sintered ceramic body as in claim 10 wherein the solid solution consists essentially of, by weight percent, 35 to 50 percent alumina, 40 to 42 percent titania, and 8 to 25 percent iron oxide. 
     
     
       12. A sintered ceramic body as in claim 10 wherein the solid solution consists essentialy of, by weight percent, 35 to 50 percent alumina, 40 to 42 percent titania, and 15 to 25 percent iron oxide.